This invention relates to a laser beam machining apparatus.
Among welding techniques for joining metals together are laser beam welding and arc welding. Laser beam welding is performed using a CO2 laser oscillator or a YAG laser oscillator. CO2 laser light has to be mirror transmitted, and thus its adjustment is laborious, while YAG laser light can be transmitted by an optical fiber. Under these circumstances, expectations are rising for laser beam welding using a YAG laser oscillator. Arc welding comes in types, including gas shielded consumable electrode arc welding (GMA welding) such as MIG welding, and gas shielded non-consumable electrode arc welding such as TIG welding.
Laser light is concentrated by an optical instrument to give a high energy density. Laser beam welding with such laser light achieves deep weld penetration in a narrow range of melting. With arc welding such as GMA welding (MIG welding, etc.) or TIG welding, on the other hand, the arc spreads in a relatively broad range, thus performing welding of a wide bead range, and enabling welding with a high groove tolerance.
In recent years, methods for simultaneously performing laser beam welding and arc welding have been studied in attempts to carry out welding with a wide welding range and a deep weld penetration.
A laser beam machining head, which performs laser welding and arc welding simultaneously, has a configuration, for example, disclosed in Japanese Unexamined Patent Publication No. 1998-216972. As shown in FIG. 14, this laser beam machining head performs laser beam welding and arc welding by applying laser light 103 from a laser beam welding head 102 to a portion 101a, to be welded, of a base metal 101, and simultaneously applying an arc discharge from an electrode 105 of a GMA welding head 104, while jetting a shielding gas at the portion 101a from a gas jet nozzle 106.
However, this laser beam machining head is large in size as a whole, since the laser beam welding head 102 and the GMA welding head 104 are independent in the laser beam machining head. Moreover, it is tiresome to keep the relative positional relationship between the laser beam welding head 102 and the GMA welding head 104 always constant in response to a change in the welding position or the welding posture. Thus, the laser beam machining head is not suitable, particularly, for three-dimensional machining by a robot.
The inventors of the present invention proposed in Japanese Unexamined Patent Publication No. 1999-156573 a laser beam machining head capable of solving the above-described problems. In this laser beam machining head, as shown in FIG. 15, laser light 112 transmitted by an optical fiber 111 is reflected by a convex roof mirror 113 and a concave roof mirror 114, and divided thereby into two divisional beams, a first divisional laser beam 112a and a second divisional laser beam 112b, with a space portion 117 being formed therebetween. These divisional laser beams 112a and 112b are focused by a focusing lens array 115 onto a portion to be welded.
The concave roof mirror 114 and the focusing lens array 115 are perforated, at the center thereof, with through-holes 114a and 115a, respectively. An electrode holding pipe 116 for holding an arc electrode, such as a TIG electrode or a GMA electrode, is inserted through the through-holes 114a, 115a, whereby the arc electrode held by the electrode holding pipe 116 is located in the space portion 117 between the divisional laser beams 112a and 112b and rendered coaxial with these laser beams.
When laser beam welding and arc welding are performed simultaneously, irradiation with laser light evaporates a metal (base metal) to ionize the metal partially (into Fe ions, Cr ions, Ni ions, etc.), and an arc discharge is induced thereby. Thus, the arc can be stabilized, so that a marked improvement in welding performance can be achieved.
To stabilize the arc reliably with laser light, however, it is necessary to control, without fail, the timing of oscillating (projecting) laser light and the timing of performing arc discharge. However, no proposal has been made for an apparatus for such control.
To carry out laser beam welding and arc welding at the same time, it is desirable to use a coaxial laser beam machining head. With the above-mentioned conventional coaxial laser beam machining head, the through-holes 114a and 115b are provided in the concave roof mirror 114 and the focusing lens array 115. Processing of these members takes much time and effort, and the through-hole portions are easily damaged. Furthermore, the convex roof mirror 113 and the concave roof mirror 114 are used to divide the laser light 112 into two beams, but these concave and convex roof mirrors 113 and 114 are very expensive.
Accordingly, the present invention has been accomplished to solve the above problems, and its challenge is to provide a laser beam machining apparatus capable of reliably stabilizing an arc when performing laser beam welding and arc welding at the same time, and having a coaxial laser beam machining head which is small in size, free from the risk of damage to optical equipment, and inexpensive.
A laser beam machining apparatus, as a first invention for solving the above challenge, is a laser beam machining apparatus adapted to perform, simultaneously, laser beam welding for welding a portion, to be welded, by transmitting and condensing laser light oscillated by a laser oscillator, and applying the laser light to the portion to be welded, and arc welding or filler wire welding for welding the portion, to be welded, by an arc discharge from an arc electrode, characterized by including
control means for exercising control such that the arc discharge from the arc electrode is performed after or simultaneously with start of oscillation of the laser light from the laser oscillator, and an output of the laser light from the laser oscillator is stopped after or simultaneously with termination of the arc discharge from the arc electrode.
According to the laser beam machining apparatus of the first invention, therefore, arc discharge can be reliably induced by laser light, and the arc can be stabilized thereby, from the start to the end of welding.
A laser beam machining apparatus of a second invention is the laser beam machining apparatus of the first invention, characterized by including
a coaxial laser beam machining head comprising the arc electrode disposed coaxially with the laser light.
According to the laser beam machining apparatus of the second invention, therefore, the laser light and the arc electrode are coaxial. Thus, the relative position of the laser light and the arc electrode is stable, and the induction of arc discharge by laser light can be performed easily.
A laser beam machining apparatus of a third invention is the laser beam machining apparatus of the second invention, characterized in that
the coaxial laser beam machining head comprises:
one collimating optical system for making the laser light into a parallel beam;
a first reflecting mirror for reflecting part of the laser light made into the parallel beam by the collimating optical system to divide the laser light into a first divisional laser beam and a second divisional laser beam;
a second reflecting mirror for further reflecting the first divisional laser beam reflected by the first reflecting mirror to form a space portion between the first divisional laser beam and the second divisional laser beam;
one focusing optical system for focusing the first divisional laser beam and the second divisional laser beam onto a portion to be machined; and
an arc electrode disposed in the space portion between the first divisional laser beam and the second divisional laser beam coaxially with the laser beams.
According to the laser beam machining apparatus of the third invention, therefore, the laser beam machining head is very small in size, inexpensive, and free from the risk of damage to the optical equipment, in comparison with the conventional laser beam machining head. This laser beam machining head is so small in size that it can be easily mounted, for example, to a multi-axis NC robot. Moreover, the arc electrode and the laser light (the first and second divisional laser beams) are coaxial. Thus, the laser beam machining head can be easily positioned and moved to an arbitrary position by the multi-axis NC robot, and three-dimensional machining can be performed with ease. Also, coaxial welding by the arc electrode and the laser light makes welding at a very high speed possible. In addition, irradiation with laser light can stabilize the arc. Thus, welding of an SUS material or a high Cr material in a pure Ar gas atmosphere becomes possible, without the use of a special wire.
A laser beam machining apparatus of a fourth invention is the laser beam machining apparatus of the third invention, characterized in that
the coaxial laser beam machining head is configured such that the second reflecting mirror is rendered normally and reversely rotatable, whereby spacing between a focused tip of the first divisional laser beam and a focused tip of the second divisional laser beam is adjustable.
According to the laser beam machining apparatus of the fourth invention, therefore, the rotation angle of the second reflecting mirror is set as desired to widen the spacing between the focused tip of the first divisional laser beam and the focused tip of the second divisional laser beam to a suitable degree, whereby a base metal with a broad gap width can be welded.
A laser beam machining apparatus of a fifth invention is the laser beam machining apparatus of the third invention, characterized in that
the coaxial laser beam machining head is configured such that the first reflecting mirror is rendered movable, whereby the division ratio for the first divisional laser beam and the second divisional laser beam can be adjusted, and the second reflecting mirror is rendered normally and reversely rotatable, whereby the spacing between the focused tip of the first divisional laser beam and the focused tip of the second divisional laser beam can be adjusted.
According to the laser beam machining apparatus of the fifth invention, therefore, the moving position of the first reflecting mirror is set as desired to decrease the proportion of the first divisional laser beam to a suitable degree and increase the proportion of the second divisional laser beam to a suitable degree, and the rotation angle of the second reflecting mirror is set as desired to widen the spacing between the focused tip of the first divisional laser beam and the focused tip of the second divisional laser beam to a suitable degree, whereby the second divisional laser beam is first applied to the base metal with a deep weld penetration, and then the first divisional laser beam is applied to form an adequate bead. On this occasion, satisfactory welding without porosity (voids) can be performed.
A laser beam machining apparatus of a sixth invention is the laser beam machining apparatus of the third, fourth or fifth invention, characterized in that
the coaxial laser beam machining head is configured such that the optical axis of the collimating optical system and the optical axis of the focusing optical system are displaced in a direction perpendicular to the optical axes, whereby the collimating optical system is moved over toward one side relative to the focusing optical system so that the first divisional laser beam reflected by the first and second reflecting mirrors is entered to the other side of the focusing optical system.
According to the laser beam machining apparatus of the sixth invention, therefore, as compared with the agreement between the optical axis of the collimating optical system and the optical axis of the focusing optical system, the first divisional laser beam and the second divisional laser beam can be focused even by the focusing optical system of a smaller diameter, and the entire laser beam machining head can be made smaller in size.
A laser beam machining apparatus of a seventh invention is the laser beam machining apparatus of the second invention, characterized in that
the coaxial laser beam machining head comprises:
one collimating optical system for making the laser light into a parallel beam;
a reflecting mirror for reflecting part of the laser light made into the parallel beam by the collimating optical system to withdraw the part of the laser light out of a body of the laser light, thereby forming a space portion in the body of the laser light;
one focusing optical system for focusing the body of the laser light, where the space portion has been formed, onto a portion to be machined; and
an arc electrode disposed in the space portion of the body of the laser light coaxially with the body of the laser light.
According to the laser beam machining apparatus of the seventh invention, therefore, the laser beam machining head is very small in size, inexpensive, and free from the risk of damage to the optical equipment, in comparison with the conventional laser beam machining head. This laser beam machining head is so small in size that it can be easily mounted, for example, to a multi-axis NC robot. Moreover, the arc electrode and the body of laser light are coaxial. Thus, the laser beam machining head can be easily positioned and moved to an arbitrary position by the multi-axis NC robot, and three-dimensional machining can be performed with ease. Also, coaxial welding makes welding at a very high speed possible. In addition, welding of an SUS material or a high Cr material in a pure Ar gas atmosphere becomes possible.
A laser beam machining apparatus of an eighth invention is the laser beam machining apparatus of the second invention, characterized in that
the coaxial laser beam machining head comprises:
one collimating optical system for making the laser light into a parallel beam;
a first reflecting mirror for reflecting part of the laser light made into the parallel beam by the collimating optical system to withdraw the part of the laser light out of a body of the laser light, thereby forming a space portion in the body of the laser light;
a second reflecting mirror located outside the body of the laser light and adapted to reflect the part of the laser light reflected by the first reflecting mirror so as to be parallel to the body of the laser light and be in contact with or in proximity to the outer peripheral surface of the body of the laser light;
one focusing optical system for focusing the body of the laser light, where the space portion has been formed by the first reflecting mirror, and the part of the laser light reflected by the first and second reflecting mirrors, onto a portion to be machined; and
an arc electrode disposed in the space portion of the body of the laser light coaxially with the body of the laser light.
According to the laser beam machining apparatus of the eighth invention, therefore, the laser beam machining head is very small in size, inexpensive, and free from the risk of damage to the optical equipment, in comparison with the conventional laser beam machining head. This laser beam machining head is so small in size that it can be easily mounted, for example, to a multi-axis NC robot. Moreover, the arc electrode and the body of laser light are coaxial. Thus, the laser beam machining head can be easily positioned and moved to an arbitrary position by the multi-axis NC robot, and three-dimensional machining can be performed with ease. Also, coaxial welding makes welding at a very high speed possible. In addition, welding of an SUS material or a high Cr material in a pure Ar gas atmosphere becomes possible. Furthermore, part of the laser light taken out of the body of the laser light by the first reflecting mirror is further reflected by the second reflecting mirror, and focused to the portion to be machined, together with the body of the laser light, by the focusing optical system. Thus, the energy of the laser light is not wasted, but can be effectively used to minimize a loss of the laser light.
A laser beam machining apparatus of a ninth invention is the laser beam machining apparatus of the eighth invention, characterized in that
the first reflecting mirror of the coaxial laser beam machining head is inserted into the laser light, which has been made into the parallel beam by the collimating optical system, along a diametrical direction of a cross sectional plane of the laser light and obliquely relative to the optical axis of the laser light, and is also inclined in a direction perpendicular to the direction of insertion of the first reflecting mirror, whereby part of the laser light is reflected obliquely to the outside of the body of the laser light.
According to the laser beam machining apparatus of the ninth invention, therefore, part of the laser light taken out of the body of the laser light is located just beside the body of the laser light. Thus, as compared with part of the laser light being located at a position displaced from the position just beside the body of the laser light, the diameter of the focusing optical system can be rendered smaller, and the entire laser beam machining head can be made smaller in size.
A laser beam machining apparatus of a tenth invention is the laser beam machining apparatus of the eighth or ninth invention, characterized in that
the coaxial laser beam machining head is configured such that the optical axis of the collimating optical system and the optical axis of the focusing optical system are displaced in a direction perpendicular to the optical axes, whereby the collimating optical system is moved over toward one side relative to the focusing optical system so that part of the laser light reflected by the first and second reflecting mirrors is entered to the other side of the focusing optical system.
According to the laser beam machining apparatus of the tenth invention, therefore, as compared with the agreement between the optical axis of the collimating optical system and the optical axis of the focusing optical system, the body of the laser light and part of the laser light can be focused even by the focusing optical system of a smaller diameter, and the entire laser beam machining head can be made smaller in size.